Let Volley's NetworkImageView show local image

问题:

I am using NetworkImageView to show some covers downloaded from a remote URL and I successfully manage to cache and show them, but I want to let users set their own cover images if they want. I tried to use setImageUrl method with Uri.fromFile(mCoverFile).toString() as arguments, but it doesn't work. Since it is a mix of remote and local images I can't switch to regular ImageViews, so I was wondering if there's any way to enable loading of local images.

I am of course aware of the ImageView's setImageBitmap method, but NetworkImageView automatically resizes the created Bitmap and also prevents View recycling in GridViews and ListViews.

UPDATE: njzk2's answer did the trick. To autoresize the Bitmap according to your View size, then just copy the ImageRequest.doParse method from Volley's source.

回答1:

NetworkImageView uses ImageLoader, which in turn uses an ImageCache.

You can provide a custom ImageCache with your images, provided you use the same mechanism for keys:

 return new StringBuilder(url.length() + 12).append("#W").append(maxWidth)
            .append("#H").append(maxHeight).append(url).toString();

url is not tested before the actual request would be done, so no issue here.

Typically, your 'cache' could look like :

public class MyCache implements ImageLoader.ImageCache {

    @Override
    public Bitmap getBitmap(String key) {
        if (key.contains("file://")) {
            return BitmapFactory.decodeFile(key.substring(key.indexOf("file://") + 7));
        } else {
            // Here you can add an actual cache
            return null;
        }
    }
    @Override
    public void putBitmap(String key, Bitmap bitmap) {
        // Here you can add an actual cache
    }
}

You use it like :

imageView.setImageUrl(Uri.fromFile(mCoverFile).toString(), new MyCache());

(This has not been actually tested and there may be some adjustments to do)

回答2:

Thank you for your answer. I wrote some code based on your help.

usage: just use LocalImageCache.class as Cache. No more code to change.

private ImageLoader mLocalImageLoader;

mLocalImageLoader = new ImageLoader(mRequestQueue,
            new LocalImageCache(mCtx));

NetworkImageView test = (NetworkImageView) findViewById(R.id.iv_test);  

test.setImageUrl("/storage/emulated/0/DCIM/Philm/2017_03_24_01_.png", MySingleton.getInstance(this.getApplicationContext()).getLocalImageLoader());

---

public class LocalImageCache extends LruCache<String, Bitmap> implements ImageLoader.ImageCache {

public LocalImageCache(int maxSize) {
    super(maxSize);
}

public LocalImageCache(Context ctx) {
    this(getCacheSize(ctx));
}

@Override
public Bitmap getBitmap(String key) {
    key = key.substring(key.indexOf("/"));
    Bitmap result = get(key);
    Log.d("TAG", key);
    if (result == null) {
        Bitmap temp =  BitmapFactory.decodeFile(key);
        put(key, temp);
        return temp;
    } else {
        return result;
    }
}

@Override
public void putBitmap(String key, Bitmap bitmap) {
    // Here you can add an actual cache
    // Never touch here
}

// 默认屏幕5倍的图片缓存
// Returns a cache size equal to approximately three screens worth of images.
public static int getCacheSize(Context ctx) {
    final DisplayMetrics displayMetrics = ctx.getResources().
            getDisplayMetrics();
    final int screenWidth = displayMetrics.widthPixels;
    final int screenHeight = displayMetrics.heightPixels;
    // 4 bytes per pixel
    final int screenBytes = screenWidth * screenHeight * 4;

    return screenBytes * 5;
}

@Override
protected int sizeOf(String key, Bitmap value) {
    return value.getRowBytes() * value.getHeight();
}

}

回答3:

NetworkImageView extends ImageView. You should be able to use the same methods as a regular ImageView

image.setImageResource(R.drawable.my_image);

or

imageView.setImageBitmap(BitmapFactory.decodeFile(imagePath));